1. Field of the Invention
The present invention relates to high-voltage, overhead, non-enclosed electric switches. More particularly, the present invention relates to a switch operator for opening and closing gang operated, high-voltage electrical switches.
2. Description of the Prior Art
Many devices for operating overhead, high-voltage air switches are known in the art. For example, Pat. No. 3,508,179 issued to Bernatt et al. on Apr. 21, 1970, Pat. No. 3,026,388 issued to Johnson on Mar. 20, 1962, Pat. No. 4,107,486 issued to Evans on Aug. 15, 1978, and Pat. No. 3,432,780 issued to Evans et al on Mar. 11, 1969 illustrate various prior art devices. Generally, these devices incorporate a ground-level mounted switch operator and a control rod or shaft that extends from the operator, along the switch pole, and then to the overhead switch. The switch operator must exert a significant force through the control rod to effect opening and closure of the switch contacts. These prior art devices are suitable for operating on three phase group operated or gang-operated switches. These types of devices, however, create the risk that workmen can become entangled in the operator mechanisms and can be injured in the event of a remote operation of the switch operator. Furthermore, the need to pre-load and post-load the control rod or shaft in order to realign a positive engagement clutching mechanism presents difficulties and hazards to workmen when coupling or decoupling the operator to conduct manual operation or motor maintenance.
Crossarm mounted operators eliminate these safety hazards and reduce the installation cost of a switch operating device. One prior art crossarm mounted switch operator is disclosed in U.S. Pat. No. 3,980,977, which issued to Evans on Sept. 14, 1976. Evans discloses the use of a coiled spring switch operator designed for use in enclosed high-voltage switches. This device incorporates a spring that is coiled or loaded by a DC motor. The loaded spring is released to apply a pre-determined force to an output shaft causing the switch contacts to change state. The coil spring operator is integral to the switch and, therefore, cannot be removed from the switch for repair or adapted to another type of switch. Furthermore, a fully coiled spring stores enough energy for several operations, but requires about ninety seconds to be recoiled. Under emergency situations, this time lag can pose a significant functional problem.
Another prior art crossarm mounted switch operator incorporates a linear ball screw coupled to a DC motor with a normally active motor brake that releases when the motor is energized. This device connects to a shaft and linkage extending from one of the rotating insulators on a switch phase of a gang operated switch. This configuration makes no provision, however, to allow the switch operator to be disengaged from the switch so that the switch can be manually operated in the event of a switch operator failure. This configuration also prevents the unit from being periodically tested and maintained without removal of the switch operator from the switch, because the switch contacts cannot remain stationary when the operator motor is exercised.
Yet another prior art device includes a "gear dog" operator as built by Kearney-KPF, Inc. This gear dog operator uses an engagement mechanism incorporating a mating set of tooth beveled gears, or "gear dogs," to couple the motor input to the output shaft of the switch operator. A compression spring supplies the force required to keep the gears engaged. A DC motor is the power source. The output shaft is connected to the phase connecting rod which, when operated, forces the rotating insulators to open the switch. This unit allows the overhead gang-operated switch to be operated manually, but does not allow the DC motor to be exercised for testing and maintenance without displacing the switch contacts. Additionally, the spring that maintains the gear dog engagement is subject to relaxation over time and could allow the gears to disengage during or after switch operation. Furthermore, realignment of the gears can be difficult after the switch has been manually operated. Notably, after manual operation the gears will often not remesh. The user must physically manipulate the switch contacts to realign the gears in order to recouple or remesh the gear dog engagement mechanism. Such conditions pose undue risks to workmen.
While the devices of the prior art fulfill their respective objectives and requirements, the prior art switch operators do not describe or suggest a crossarm mounted switch operator that incorporates an infinite engagement clutch coupling mechanism that allows for manual operation of the switch and for testing and maintenance of the switch operator without the disadvantages associated with prior art devices. Namely, the switch operator of the present invention allows the user to effectively engage and/or disengage the switch operator without the alignment, pre-loading, and post-loading problems associated with the prior art devices described above. In this respect, the switch operator according to the present invention represents a substantial improvement over the concepts and switch operator designs of the prior art, and in doing so provides a novel switch operator having an infinite engagement clutch coupling mechanism primarily developed for operating overhead, gang-operated switches and allowing manual operation and testing thereof without movement of the switch contacts. Therefore, it can be appreciated that a need exists for a new switch operator that employs an infinite engagement clutch coupling mechanism which eliminates the alignment, pre-loading and post-loading problems of the prior art. In this regard, the present invention substantially fulfills these needs.